1. Technical Field
The present invention relates to a folder binding device, and more particularly, to a flat folder binding device for use in binding sheets of paper having binding holes formed therein with a pair of binding strips or legs.
2. Background Art
In general, a flat folder for binding sheets of paper having binding holes formed therein is such that binding strips or legs fixed to the folder are inserted and passed through the binding holes in sheets of paper, so that the binding legs are fastened by a binding device. In this flat folder, after the flexible binding legs have been passed through binding holes in sheets of paper, the flexible binding legs are inserted further into holes in a binding device main body, and the binding legs which projects from the binding device main body are then fastened and unfastened by moving horizontally sliding members which are attached slidably to the binding device main body.
In the binding device of this type, since the unfastening and fastening operations are implemented by horizontally moving the sliding members while pressing them, a certain magnitude of force is required. In addition, the unfastening and fastening operations have to be carried out repeatedly every time a sheet or sheets of paper are bound, which is found troublesome to the user. Then, as a binding device which can be operated with slight force without moving sliding members while pressing them, there has been proposed a binding device in which binding legs are fastened and unfastened by a rotary member attached to a binding device main body. Japanese Examined Utility Model Publication No. 57-55105 proposes a binding device which comprises a binding device main body which includes insertion holes through which binding legs are inserted and pressing elements which are rotatably supported on the binding device main body. This proposed binding device is such that the pressing elements open and close binding leg insertion holes to unfasten and fasten the binding legs. In addition, Japanese Unexamined Patent Publication No. 2003-11565 proposes a binding device which comprises a binding device main body having a bearing part and pressing elements having shafts at distal ends of two arms, wherein the pressing elements are mounted rotatably in the bearing part. In this proposed binding device, an inner surface of the bearing part is made into an inclined surface, and the shafts of the pressing elements are also made into inclined surfaces, whereby a supporting construction is provided in which when the arms of the pressing elements return outwards by virtue of elastic force in such a state that the inclined surfaces of the shafts are in surface contact with the inner surface of the bearing part, the pressing elements return to an unfastened angular position by being guided by the inclined surfaces.